Photopolymers and Their Use in Organic Thin Film Transistors

ABSTRACT

Photopolymers are provided with composites and electronic devices including such photopolymers. Specifically, organic thin film transistors comprising a semiconductor layer, a polymeric layer in contact with the semiconductor layer, a gate electrode, a source electrode and a drain electrode are disclosed, wherein the semiconductor layer comprises an organic semiconductor compound, and the polymeric layer comprises a photocrosslinked product of a photopolymer.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.11/998,159, filed on Nov. 28, 2007, which claims priority to and thebenefit of U.S. Provisional Patent Application Ser. No. 60/861,308,filed on Nov. 28, 2006, the disclosure of each of which is incorporatedby reference herein in its entirety.

INTRODUCTION

The development of polymeric dielectric materials has been fundamentalfor the progress of organic electronic devices. In particular, emergingdisplay and identification/tracking/labeling technologies based onorganic thin-film transistors (OTFTs), such as electronic paper andradiofrequency identification (RFID) devices, require fabrication ofOTFTs on plastic, paper, or other flexible substrates over very largeareas and via high throughput processes. Therefore, there has beenconsiderable effort in developing new materials for OTFT components(semiconductor, dielectric, and contacts) which can be deposited viasolution-processing methods such as spin-coating, casting, and printing.

Although various polymers have been employed as dielectrics for OTFTs,several limitations of current-generation polymeric dielectric-basedOTFTs exist. First, the leakage current densities of conventionalpolymeric dielectric films are relatively high (usually >1×10⁻⁷ A/cm² at2 MV/cm, >>1×10⁻⁵ A/cm² at 4 MV/cm). Second, very few polymericdielectric materials are sufficiently soluble to be solution-processed,especially via inexpensive printing techniques. Among those that aresolution-processable, they often cannot survive the conditions used insubsequent solution-processing steps (e.g., for TFT device fabrication,the deposition of overlying layers such as the semiconductor layer (forbottom-gate devices), the conductor layer, and the passive layers),hence their application in device fabrication is significantly limited.Third, currently available polymeric dielectric materials often fail toachieve a sub-nanometer/nanometer surface smoothness, which is aprerequisite for stable TFT performance and operation.

To address these issues, crosslinkable polymeric dielectrics such ascrosslinked melamine/Cr⁶⁺ salts-polyvinylphenol (PVP) and crosslinkedbenzocyclobutene (BCB) have been introduced. However, these polymerfilms require high annealing temperatures and their leakage currentdensities are usually higher than 10⁻⁷ A/cm² at 2 MV/cm. The highcurrent leakage densities of these polymeric dielectrics are believed tobe due to, among other factors, the hydrophilic nature of phenol-basedpolymers and the presence of crosslinker additives.

On the other hand, polymers with a hydrophobic backbone such aspoly(methylmethacrylate) (PMMA) and polystyrene offer the possibility ofachieving much lower TFT gate leakage current densities and greaterenvironmental stability. These hydrophobic polymers are often soluble incommon organic solvents but, because of the lack of crosslinkingfunctionality, they cannot withstand subsequent solution-phaseprocessing steps in which additional layers are deposited.

Accordingly, there is a desire in the art for crosslinkable polymericdielectric materials that can exhibit low current leakage densities,that can be prepared via solution processes, that can be air- and/ormoisture-stable, and that can be compatible with diverse gate and/orsemiconductor materials.

SUMMARY

In light of the foregoing, the present teachings providephotopolymer-based dielectric materials (e.g. films) and associateddevices that can address various deficiencies and shortcomings of theprior art, including those outlined above.

In one aspect, the present teachings provide photopolymers that can beused to prepare dielectric materials. Among other desirable properties,polymers of the present teachings can be soluble in common organicsolvents but can become insoluble in the same solvents after undergoingcrosslinking, for example, photocrosslinking, which gives rise tocertain processing advantages. More specifically, the present teachingsprovide polymers having crosslinkable functional groups, for example,photocrosslinkable functional groups, that allow the polymers tocrosslink. The crosslinking functionality can allow formation of adensely crosslinked polymeric matrix. Photopolymers of the presentteachings and their crosslinked products can have excellent insulatingproperties, which enable their use as dielectrics. In some embodiments,the photopolymers and their crosslinked products can have a leakagecurrent density that is less than or equals to about 1×10⁻⁸ A/cm² at 2MV/cm.

Polymers of the present teachings can have a pendant group having theformula:

wherein R¹, R², L, and Z are as defined herein. In certain embodiments,the present teachings provide polymers having the formula:

wherein R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, L, L′, W, Z, m, and n are asdefined herein.

The present teachings also provide dielectric materials that include thepolymers described above. For example, the dielectric materials can beprepared from the polymers described above. Multilayer dielectricmaterials are provided which include two or more layers of dielectricmaterials sequentially deposited on top of each other, where at leastone of the layers is prepared from polymers of the present teachings.These photopolymers can be used to prepare dielectric materials usingvarious solution processes, including various printing techniques.

The present teachings further provide electronic devices that include orare made from any of the dielectric materials described above. Examplesof electronic devices include, but are not limited to, organic thin filmtransistors (OTFTs) (e.g., organic field effect transistors (OFETs)) andcapacitors. In addition to a dielectric component, these devices caninclude, for example, a substrate component, a semiconductor component,and/or a metallic contact component.

Methods for preparing the polymers, the dielectric materials, and theelectronic devices described above are also provided and are within thescope of the present teachings.

The foregoing as well as other features and advantages of the presentteachings will be more fully understood from the following figures,description, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

It should be understood that the drawings described below are forillustration purposes only and are not necessarily to scale. Thedrawings are not intended to limit the scope of the present teachings inany way.

FIG. 1 provides leakage current density (J) versus electric field (E)plots of various metal-insulator-semiconductor capacitor structures ofdifferent feature sizes in which the insulating layer is a dielectricmaterial of the present teachings [P(CyVP_(0.55)-co-MMA_(0.45))].

FIG. 2 provides leakage current density (J) versus electric field (E)plots of various metal-insulator-semiconductor capacitor structures thatwere fabricated using dielectric materials of the present teachings andother comparative dielectric materials.

FIG. 3 provides leakage current density (J) versus electric field (E)plots of various metal-insulator-semiconductor capacitor structures thatwere fabricated using dielectric materials of the present teachings andother comparative dielectric materials.

FIG. 4 provides representative transfer and output plots ofpentacene-based organic field effect transistors fabricated withspin-coated dielectric materials of the present teachings[P(CyEMA_(0.57)-co-F5BEMA_(0.43))].

FIG. 5 provides representative transfer and output plots of n-typeorganic field effect transistors fabricated with spin-coated dielectricmaterials of the present teachings [P(CyVP_(0.55)-co-MMA_(0.45))].

FIG. 6 provides a leakage current density (J) versus electric field (E)plot of a metal-insulator-semiconductor capacitor structure thatincorporates a two-layer dielectric material of the present teachings[P(CyVP_(0.55)-co-MMA_(0.45))].

FIG. 7 provides representative transfer and output plots of apentacene-based organic field effect transistor that incorporates amultilayer dielectric material of the present teachings[P(CyVP_(0.55)-co-MMA_(0.45))].

FIG. 8 provides representative transfer and output plots ofpentacene-based organic field effect transistors fabricated with printeddielectric materials of the present teachings[P(CyEMA_(0.80)-co-AcEMA_(0.20))].

FIG. 9 shows an IR absorption spectrum of a dielectric material of thepresent teachings before and after crosslinking.

FIG. 10 shows a typical DSC plot of a polymer of the present teachings.

FIG. 11 shows a leakage current density (J) versus electric field (E)plot of a metal-insulator-semiconductor capacitor structure thatincorporates a dielectric material of the present teachings having beenstored in air for 55 days.

FIG. 12 provides representative transfer and output plots of an organicfield effect transistor that incorporates a printed dielectric materialof the present teachings and a drop-cast semiconductor layer preparedfrom N,N′-bis(n-octyl)-dicyanoperylene-3,4:9,10-bis(dicarboximide)(PDI-8CN₂).

FIG. 13 provides a leakage current density (J) versus electric field (E)plot of a metal-insulator-semiconductor capacitor structure thatincorporates a dielectric material of the present teachings having afilm thickness of 100 nm.

FIG. 14 provides leakage current density (J) versus electric field (E)plots of various metal-insulator-semiconductor capacitor structures thatwere fabricated using a dielectric material of the present teachings[P(CyVP_(0.55)-co-MMA_(0.45))] and a comparative dielectric material[P(VP_(0.30)-co-CyVP_(0.25)-co-MMA_(0.45))].

FIG. 15 provides leakage current density (J) versus electric field (E)plots of metal-insulator-semiconductor capacitor structures that werefabricated using spin-coated dielectric materials of the presentteachings (photopatterned and rinsed versus no photopatterning/rinsing).

FIG. 16 illustrates different configurations of organic field effecttransistors.

FIG. 17 provides representative transfer and output plots of abottom-contact bottom-gate organic field effect transistor thatincorporates a spin-coated dielectric material of the present teachingsand a vapor-deposited semiconductor layer prepared from pentacene.

FIG. 18 provides a representative transfer plot of a bottom-contacttop-gate organic field effect transistor that incorporates a spin-coateddielectric material of the present teachings and a vapor-depositedsemiconductor layer prepared from pentacene.

FIG. 19 provides a representative output plot of a top-contactbottom-gate organic field effect transistor that incorporates aspin-coated dielectric material of the present teachings and aconducting polymer as the bottom-gate electrode.

DETAILED DESCRIPTION

The present teachings relate to photopolymers that can be used toprepare dielectric materials, the dielectric materials so prepared,methods for preparing the photopolymers and the dielectric materials, aswell as to compositions, articles, structures, and devices that includesuch photopolymers and dielectric materials.

More specifically, the present teachings provide solution-processablepolymers that can be crosslinked, for example, photocrosslinked, toprovide insoluble robust dielectric materials that can exhibit excellentinsulating properties and can be used to fabricate various organicelectronic devices, including OTFTs. The dielectric materials also canbe air-stable and have long shelf stability, and can be compatible witha wide range of p-type and n-type organic and inorganic semiconductors,making them attractive materials for fabricating various organicelectronic devices.

Throughout the description, where compositions are described as having,including, or comprising specific components, or where processes aredescribed as having, including, or comprising specific process steps, itis contemplated that compositions of the present teachings also consistessentially of, or consist of, the recited components, and that theprocesses of the present teachings also consist essentially of, orconsist of, the recited process steps.

In the application, where an element or component is said to be includedin and/or selected from a list of recited elements or components, itshould be understood that the element or component can be any one of therecited elements or components and can be selected from a groupconsisting of two or more of the recited elements or components.Further, it should be understood that elements and/or features of acomposition, an apparatus, or a method described herein can be combinedin a variety of ways without departing from the spirit and scope of thepresent teachings, whether explicit or implicit herein.

The use of the terms “include,” “includes,” “including,” “have,” “has,”or “having” should be generally understood as open-ended andnon-limiting unless specifically stated otherwise.

The use of the singular herein includes the plural (and vice versa)unless specifically stated otherwise. In addition, where the use of theterm “about” is before a quantitative value, the present teachings alsoinclude the specific quantitative value itself, unless specificallystated otherwise. As used herein, the term “about” refers to a ±10%variation from the nominal value.

It should be understood that the order of steps or order for performingcertain actions is immaterial so long as the present teachings remainoperable. Moreover, two or more steps or actions may be conductedsimultaneously.

As used herein, “polymer” or “polymeric compound” refers to a moleculeconsisting of at least two repeating units (monomers) connected bycovalent chemical bonds. The polymer or polymeric compound can have onlyone type of repeating unit as well as two or more types of differentrepeating units. In the latter case, the term “copolymer” or“copolymeric compound” can be used instead, especially when the polymerincludes chemically significantly different repeating units. A polymertypically comprises a backbone with optional pendant groups. Unlessspecified otherwise, the assembly of the repeating units in thecopolymer can be head-to-tail, head-to-head, or tail-to-tail. Inaddition, unless specified otherwise, the copolymer can be a randomcopolymer, an alternating copolymer, or a block copolymer. In someembodiments, formulae similar to the ones below can be used to representa copolymer, and such formula should be interpreted to embrace acopolymer having any repeating pattern consisting of x % of Q¹, y % ofQ², and z % of Q³, where Q¹, Q², and Q³ are different repeating units:

As used herein, a “pendant group” refers to a moiety that is substitutedon the backbone of a polymer.

As used herein, “photopolymer” refers to a polymer that can be cured,for example, crosslinked, by exposure to light, often in the ultravioletregion of the spectrum, or other types of radiation.

As used herein, “solution-processable” refers to compounds, materials,or compositions that can be used in various solution-phase processesincluding, but not limited to, spin-coating, printing (e.g., inkjetprinting), spray coating, electrospray coating, drop casting, dipcoating, and blade coating.

As used herein, “halo” or “halogen” refers to fluoro, chloro, bromo, andiodo.

As used herein, “amino” refers to —NH₂, an —NH-alkyl group, an—N(alkyl)₂ group, an —NH-arylalkyl group, an —N(alkyl)-arylalkyl group,and an —N(arylalkyl)₂ group, and is within the definition of —NR¹R²,wherein R¹ and R² are as defined herein.

As used herein, “alkoxy” refers to —O-alkyl group, and is within thedefinition of —OR³, wherein R³ is as defined herein. Examples of alkoxygroups include, but are not limited to, methoxy, ethoxy, propoxy (e.g.,n-propoxy and isopropoxy), t-butoxy groups, and the like.

As used herein, “alkylthio” refers to an —S-alkyl group. Examples ofalkylthio groups include, but are not limited to, methylthio, ethylthio,propylthio (e.g., n-propylthio and isopropylthio), t-butylthio groups,and the like.

As used herein, “ester” refers to both an —O—C(O)-alkyl group and a—C(O)—O-alkyl group, where the former group is within the definition of—OC(O)R³, and R³ is as defined herein.

As used herein, “oxo” refers to a double-bonded oxygen (i.e., ═O).

As used herein, “alkyl” refers to a straight-chain or branched saturatedhydrocarbon group. Examples of alkyl groups include methyl (Me), ethyl(Et), propyl (e.g., n-propyl and isopropyl), butyl (e.g., n-butyl,isobutyl, sec-butyl, tert-butyl), pentyl groups (e.g., n-pentyl,isopentyl, neopentyl), and the like. In various embodiments, an alkylgroup can have 1 to 30 carbon atoms, i.e., a C₁₋₃₀ alkyl group, and, forexample, an alkyl group can have 1 to 20 carbon atoms, i.e., a C₁₋₂₀alkyl group. In some embodiments, an alkyl group can have 1 to 6 carbonatoms, and can be referred to as a “lower alkyl group.” Examples oflower alkyl groups include methyl, ethyl, propyl (e.g., n-propyl andisopropyl), and butyl groups (e.g., n-butyl, isobutyl, sec-butyl,tert-butyl). In some embodiments, alkyl groups can be substituted asdisclosed herein.

As used herein, “haloalkyl” refers to an alkyl group having one or morehalogen substituents. Examples of haloalkyl groups include, but are notlimited to, CF₃, C₂F₅, CHF₂, CH₂F, CCl₃, CHCl₂, CH₂Cl, C₂Cl₅, and thelike. Perhaloalkyl groups, i.e., alkyl groups wherein all of thehydrogen atoms are replaced with halogen atoms (e.g., CF₃ and C₂F₅), areincluded within the definition of “haloalkyl.” For example, a C₁₋₂₀haloalkyl group can have the formula —C_(n)X_(2n+1) or—C_(n)H_(2n+1-t)X_(t), wherein X is F, Cl, Br, or I, n is an integer inthe range of 1 to 20, and t is an integer in the range of 0 to 41,provided that t is less than or equal to 2n+1.

As used herein, “alkenyl” refers to a straight-chain or branched alkylgroup having one or more carbon-carbon double bonds. Examples of alkenylgroups include, but are not limited to, ethenyl, propenyl, butenyl,pentenyl, hexenyl, butadienyl, pentadienyl, hexadienyl groups, and thelike. The one or more carbon-carbon double bonds can be internal (suchas in 2-butene) or terminal (such as in 1-butene). In variousembodiments, an alkenyl group can have 2 to 20 carbon atoms, i.e., aC₂₋₂₀ alkenyl group. In some embodiments, alkenyl groups can besubstituted as disclosed herein.

As used herein, “alkynyl” refers to a straight-chain or branched alkylgroup having one or more triple carbon-carbon bonds. Examples of alkynylgroups include, but are not limited to, ethynyl, propynyl, butynyl,pentynyl, and the like. The one or more triple carbon-carbon bonds canbe internal (such as in 2-butyne) or terminal (such as in 1-butyne). Invarious embodiments, an alkynyl group can have 2 to 20 carbon atoms,i.e., a C₂₋₂₀ alkynyl group. In some embodiments, alkynyl groups can besubstituted as disclosed herein.

As used herein, “cycloalkyl” refers to a non-aromatic carbocyclic groupincluding cyclized alkyl, alkenyl, and alkynyl groups. A cycloalkylgroup can be monocyclic (e.g., cyclohexyl) or polycyclic (e.g.,containing fused, bridged, and/or spiro ring systems), wherein thecarbon atoms are located inside or outside of the ring system. Anysuitable ring position of the cycloalkyl group can be covalently linkedto the defined chemical structure. Examples of cycloalkyl groupsinclude, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl,cyclohexyl, cycloheptyl, cyclopentenyl, cyclohexenyl, cyclohexadienyl,cycloheptatrienyl, norbornyl, norpinyl, norcaryl, adamantyl, andspiro[4.5]decanyl groups, as well as their homologs, isomers, and thelike. In various embodiments, a cycloalkyl group can have 3 to 14 carbonatoms, including 3 to 10 carbon atoms (i.e., a C₃₋₁₀ cycloalkyl group).In some embodiments, cycloalkyl groups can be substituted as disclosedherein.

As used herein, “heteroatom” refers to an atom of any element other thancarbon or hydrogen and includes, for example, nitrogen, oxygen, silicon,sulfur, phosphorus, and selenium.

As used herein, “cycloheteroalkyl” refers to a non-aromatic cycloalkylgroup that contains at least one ring heteroatom selected from O, N, andS, and optionally contains one or more double or triple bonds. Invarious embodiments, a cycloheteroalkyl group can have 3 to 20 ringatoms, including 3 to 14 ring atoms (i.e., a 3-14 memberedcycloheteroalkyl group). One or more N or S atoms in a cycloheteroalkylring may be oxidized (e.g., morpholine N-oxide, thiomorpholine S-oxide,thiomorpholine S,S-dioxide). In some embodiments, nitrogen atoms ofcycloheteroalkyl groups can bear a substituent, for example, a hydrogenatom, an alkyl group, or other substituents as described herein.Cycloheteroalkyl groups can also contain one or more oxo groups, such asoxopiperidyl, oxooxazolidyl, dioxo-(1H,3H)-pyrimidyl, oxo-2(1H)-pyridyl,and the like. Examples of cycloheteroalkyl groups include, among others,morpholinyl, thiomorpholinyl, pyranyl, imidazolidinyl, imidazolinyl,oxazolidinyl, pyrazolidinyl, pyrazolinyl, pyrrolidinyl, pyrrolinyl,tetrahydrofuranyl, tetrahydrothiophenyl, piperidinyl, piperazinyl, andthe like. In some embodiments, cycloheteroalkyl groups can besubstituted as disclosed herein.

As used herein, “aryl” refers to an aromatic monocyclic hydrocarbon ringsystem or a polycyclic ring system in which two or more aromatichydrocarbon rings are fused (i.e., having a bond in common with)together or at least one aromatic monocyclic hydrocarbon ring is fusedto one or more cycloalkyl and/or cycloheteroalkyl rings. An aryl groupcan have from 6 to 14 carbon atoms in its ring system, which can includemultiple fused rings. In some embodiments, a polycyclic aryl group canhave from 7 to 14 carbon atoms. Any suitable ring position of the arylgroup can be covalently linked to the defined chemical structure.Examples of aryl groups having only aromatic carbocyclic ring(s)include, but are not limited to, phenyl, 1-naphthyl (bicyclic),2-naphthyl (bicyclic), anthracenyl (tricyclic), phenanthrenyl(tricyclic), and like groups. Examples of polycyclic ring systems inwhich at least one aromatic carbocyclic ring is fused to one or morecycloalkyl and/or cycloheteroalkyl rings include, among others, benzoderivatives of cyclopentane (i.e., an indanyl group, which is a5,6-bicyclic cycloalkyl/aromatic ring system), cyclohexane (i.e., atetrahydronaphthyl group, which is a 6,6-bicyclic cycloalkyl/aromaticring system), imidazoline (i.e., a benzimidazolinyl group, which is a5,6-bicyclic cycloheteroalkyl/aromatic ring system), and pyran (i.e., achromenyl group, which is a 6,6-bicyclic cycloheteroalkyl/aromatic ringsystem). Other examples of aryl groups include, but are not limited to,benzodioxanyl, benzodioxolyl, chromanyl, indolinyl groups, and the like.In some embodiments, aryl groups can be substituted with up to fivesubstitution groups as disclosed herein. For example, an aryl group canbe substituted with one to five halogen substituents and such an arylgroup can be referred to as a “haloaryl” group. An example of a haloarylgroup is a perhalophenyl group, where the phenyl group is substitutedwith five halogen atoms.

As used herein, “heteroaryl” refers to an aromatic monocyclic ringsystem containing at least 1 ring heteroatom selected from oxygen (O),nitrogen (N), and sulfur (S) or a polycyclic ring system where at leastone of the rings present in the ring system is aromatic and contains atleast 1 ring heteroatom. Polycyclic heteroaryl groups include two ormore heteroaryl rings fused together and monocyclic heteroaryl ringsfused to one or more aromatic carbocyclic rings (aryl groups),non-aromatic carbocyclic rings (cycloalkyl groups), and/or non-aromaticcycloheteroalkyl groups. A heteroaryl group, as a whole, can have, forexample, from 5 to 14 ring atoms and contain 1-5 ring heteroatoms. Theheteroaryl group can be attached to the defined chemical structure atany heteroatom or carbon atom that results in a stable structure.Generally, heteroaryl rings do not contain O—O, S—S, or S—O bonds.However, one or more N or S atoms in a heteroaryl group can be oxidized(e.g., pyridine N-oxide, thiophene S-oxide, thiophene S,S-dioxide).Examples of heteroaryl groups include, for example, the 5-memberedmonocyclic and 5-6 bicyclic ring systems shown below:

where T is O, S, NH, N-alkyl, N-aryl, or N-(arylalkyl) (e.g., N-benzyl).Examples of heteroaryl groups include pyrrolyl, furyl, thienyl, pyridyl,pyrimidyl, pyridazinyl, pyrazinyl, triazolyl, tetrazolyl, pyrazolyl,imidazolyl, isothiazolyl, thiazolyl, thiadiazolyl, isoxazolyl, oxazolyl,oxadiazolyl, indolyl, isoindolyl, benzofuryl, benzothienyl, quinolyl,2-methylquinolyl, isoquinolyl, quinoxalyl, quinazolyl, benzotriazolyl,benzimidazolyl, benzothiazolyl, benzisothiazolyl, benzisoxazolyl,benzoxadiazolyl, benzoxazolyl, cinnolinyl, 1H-indazolyl, 2H-indazolyl,indolizinyl, isobenzofuyl, naphthyridinyl, phthalazinyl, pteridinyl,purinyl, oxazolopyridinyl, thiazolopyridinyl, imidazopyridinyl,furopyridinyl, thienopyridinyl, pyridopyrimidinyl, pyridopyrazinyl,pyridopyridazinyl, thienothiazolyl, thienoxazolyl, thienoimidazolyl, andthe like. Further examples of heteroaryl groups include, but are notlimited to, 4,5,6,7-tetrahydroindolyl, tetrahydroquinolyl,benzothienopyridyl, benzofuropyridyl, and the like. In some embodiments,heteroaryl groups can be substituted as disclosed herein.

Compounds of the present teachings can include a “divalent group”defined herein as a linking group capable of forming a covalent bondwith two other moieties. For example, compounds of the present teachingscan include, but are not limited to, a divalent C₁₋₂₀ alkyl group suchas a methylene group.

As used herein, a “leaving group” (“LG”) refers to a charged oruncharged atom (or group of atoms) that can be displaced as a stablespecies as a result of, for example, a substitution or eliminationreaction. Examples of leaving groups include, but are not limited to,halide (e.g., Cl, Br, I), tosylate (toluenesulfonyl group, TsO),mesylate (methanesulfonyl group, MsO), brosylate (p-bromobenzenesulfonylgroup, BsO), nosylate (4-nitrobenzenesulfonyl group, NsO), water (H₂O),ammonia (NH₃), and triflate (trifluoromethanesulfonyl group, OTf).

At various places in the present specification, substituents ofcompounds are disclosed in groups or in ranges. It is specificallyintended that the description include each and every individualsubcombination of the members of such groups and ranges. For example,the term “C₁₋₆ alkyl” is specifically intended to individually discloseC₁, C₂, C₃, C₄, C₅, C₆, C₁-C₆, C₁-C₅, C₁-C₄, C₁-C₃, C₁-C₂, C₂-C₆, C₂-C₅,C₂-C₄, C₂-C₃, C₃-C₆, C₃-C₅, C₃-C₄, C₄-C₆, C₄-C₅, and C₅-C₆ alkyl. By wayof other examples, an integer in the range of 0 to 40 is specificallyintended to individually disclose 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29,30, 31, 32, 33, 34, 35, 36, 37, 38, 39, and 40, and an integer in therange of 1 to 20 is specifically intended to individually disclose 1, 2,3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20.

Throughout the specification, structures may or may not be presentedwith chemical names. Where any question arises as to nomenclature, thestructure prevails.

In one aspect, the present teachings provide photopolymers that includeone or more crosslinkable functionalities. The crosslinking group canform or be a portion of a pendant group covalently attached to thebackbone of the polymers. More specifically, the present teachingsprovide a polymer including a pendant group having the formula:

wherein:

-   L, at each occurrence, is independently —Y, —Y—O—Y—, -Q-, —Y—S—Y—,    —Y—C(O)—O—Y—, -Q-C(O)—O—Y—, —Y—O—C(O)-Q-, —Y—O—C(O)—Y—, -Q-C(O)-Q-,    —Y—C(O)—Y—, -Q-C(O)—Y—, or —Y—C(O)-Q-;

wherein:

Q, at each occurrence, is —O—[Y—O]_(p)—Y—O—;

Y, at each occurrence, is a divalent C₁₋₁₀ alkyl group, a divalent C₂₋₁₀alkenyl group, a divalent C₂₋₁₀ alkynyl group, a divalent C₆₋₁₀ arylgroup, or a covalent bond, wherein each of the C₁₋₁₀ alkyl group, theC₂₋₁₀ alkenyl group, the C₂₋₁₀ alkynyl group, and the C₆₋₁₀ aryl groupis optionally substituted with 1 to 5 substituents independentlyselected from a halogen and CN; and

p is an integer in the range of 0 to 10;

-   R¹ and R² are independently H, a halogen, or CN; and-   Z is a C₁₋₁₀ alkyl group, a C₁₋₁₀ haloalkyl group, or a C₆₋₁₀ aryl    group optionally substituted with 1 to 5 substituents independently    selected from a halogen, CN, a C₁₋₂₀ alkyl group,-   a C₁₋₂₀ haloalkyl group, a C₁₋₂₀ alkoxy group, a —O—C₁₋₂₀ haloalkyl    group, a —C(O)—C₁₋₆ alkyl group, a —C(O)—C₁₋₆ haloalkyl group, and a    —C(O)—O—C₁₋₆ alkyl group.

In some embodiments, R¹ and R² can be independently H or F. In certainembodiments, Z can be a C₁₋₆ alkyl group, a C₁₋₆ perfluoroalkyl group,or a phenyl group optionally substituted with 1 to 5 substituentsindependently selected from a halogen such as F, a C₁₋₂₀ alkyl group, aC₁₋₂₀ haloalkyl group, a C₁₋₂₀ alkoxy group, and a —O—C₁₋₂₀ haloalkylgroup. For example, Z can be a phenyl group, a perhalophenyl group, or aphenyl group substituted with a trifluoromethyl group, a C₁₋₂₀ alkoxygroup, or a —O—C₁₋₂₀ haloalkyl group. In some embodiments, L, at eachoccurrence, can be independently —O—, —C₆H₅—O—, —C(O)—O—,—C(O)—O—CH₂CH₂—O—, —C(O)—O—CF₂CF₂—O—, or a covalent bond.

In various embodiments, polymers of the present teachings can have arepeating unit having the formula:

wherein:

-   R³, R⁴, and R⁵ are independently H, a halogen, a C₁₋₁₀ alkyl group,    or a C₆₋₁₄ aryl group, wherein each of the C₁₋₁₀ alkyl group and the    C₆₋₁₄ aryl group is optionally substituted with 1 to 5 substituents    independently selected from a halogen and CN; and-   R¹, R², L, and Z are as defined herein.

In some embodiments, polymers of the present teachings can have arepeating unit having a formula selected from:

wherein R¹, R², R³, and Z are as defined herein. For example, polymersof the present teachings can have a repeating unit having the formula:

wherein:

U is —Y— or —Y—O—Y—;

-   R¹² is H, a C₁₋₂₀ alkyl group, or a C₁₋₂₀ haloalkyl group; and-   Y is as defined herein.

In some embodiments, U can be —O— or a covalent bond. In someembodiments, R¹² can be H, —CF₃, a hexyl group, a decyl group, anoctadecyl group, or —(CH₂)₃(CF₂)₇CF₃. For example, polymers of thepresent teachings can have a repeating unit selected from:

In various embodiments, polymers of the present teachings can have theformula:

wherein:

-   R⁶, R⁷, and R⁸ are independently H, a halogen, a C₁₋₁₀ alkyl group,    or a C₆₋₁₄ aryl group, wherein each of the C₁₋₁₀ alkyl group and the    C₆₋₁₄ aryl group is optionally substituted with 1 to 5 substituents    independently selected from a halogen and CN;-   L′ is —Y—, —Y—O—Y—, -Q-, —Y—S—Y—, —Y—C(O)—O—Y—, -Q-C(O)—O—Y—,    —Y—O—C(O)-Q-, —Y—O—C(O)—Y—, -Q-C(O)-Q-, —Y—C(O)—Y—, -Q-C(O)—Y—, or    —Y—C(O)-Q-;-   W is a C₁₋₁₀ alkyl group, a C₁₋₁₀ haloalkyl group, a C₁₋₁₀ alkoxy    group, or a C₆₋₁₀ aryl group optionally substituted with 1 to 5    substituents independently selected from a halogen, CN, a C₁₋₆ alkyl    group, a C₁₋₆ haloalkyl group, a C₁₋₆ alkoxy group, a —C(O)—C₁₋₆    alkyl group, a —C(O)—C₁₋₆ haloalkyl group, and a —C(O)—O—C₁₋₆ alkyl    group;-   m and n are independently a real number, wherein 0<m≦1, 0≦n<1, and    m+n=1; and R¹, R², R³, R⁴, R⁵, L, Q, Y, and Z are as defined herein.

In some embodiments, the polymers can have the formula:

wherein R¹, R², R³, R⁶, W, Z, m, and n are as defined herein.

For example, the polymers can have a formula selected from:

wherein m and n are as defined herein.

In some embodiments, the polymer can have the formula:

wherein m, n, R¹², and U are as defined herein.

For example, the polymer can have a formula selected from:

wherein m and n are as defined herein.

In some embodiments, the polymer can have the formula:

wherein:

-   R⁹, R¹⁰, and R¹¹ are independently H, a halogen, a C₁₋₁₀ alkyl    group, or a C₆₋₁₄ aryl group, wherein each of the C₁₋₁₀ alkyl group    and the C₆₋₁₄ aryl group is optionally substituted with 1 to 5    substituents independently selected from a halogen and CN;-   W′ is a C₁₋₁₀ alkyl group, a C₁₋₁₀ haloalkyl group, a C₁₋₁₀ alkoxy    group, or a C₆₋₁₀ aryl group optionally substituted with 1 to 5    substituents independently selected from a halogen, CN, a C₁₋₆ alkyl    group, a C₁₋₆ haloalkyl group, a C₁₋₆ alkoxy group, a —C(O)—C₁₋₆    alkyl group, a —C(O)—C₁₋₆ haloalkyl group, and a —C(O)—O—C₁₋₆ alkyl    group;-   m′, n′, and n″ are independently a real number, wherein 0<m′≦1,    0≦n′<1, 0≦n″<1, and m′+n′+n″=1; and-   R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, L, L′, W, and Z are as defined    herein.

In certain embodiments, W′ can be a C₁₋₆ alkyl group, a C₁₋₆ haloalkylgroup, or a C₆₋₁₀ aryl group optionally substituted with 1 to 5substituents independently selected from a halogen, CN, a C₁₋₆ alkylgroup, a C₁₋₆ haloalkyl group, a C₁₋₆ alkoxy group, a —C(O)—C₁₋₆ alkylgroup, a —C(O)—C₁₋₆ haloalkyl group, and a —C(O)—O—C₁₋₆ alkyl group. Forexample, W′ can be a C₁₋₆ alkyl group or a C₁₋₆ haloalkyl group. Inparticular embodiments, W′ can be CF₃.

Polymers of the present teachings can include, but are not limited to,the polymers below:

Photopolymers of the present teachings can be synthesized followingScheme 1 below. Other synthetic routes, including known to those skilledin the art, also can be used.

In the scheme above, the desired pendant group can be coupled to apolymer, for example, a hydrophobic polymeric backbone, by reactingnucleophilic groups on the polymer with an acyl chloride, an acylanhydride, or similar derivatives and groups that can form covalentbonds with nucleophilic groups, for example, electrophilic groups.Without wishing to be bound to any particular theory, it is believedthat by derivatizing the OH groups of the polymer to other less acidicgroups, polymers of the present teachings can have lower currentleakages, as well as improved shelf stability. In some embodiments,

The polymers disclosed herein can have satisfactory solubility in commonorganic solvents. Examples of common organic solvents include, but arenot limited to, petroleum ethers; aromatic hydrocarbons such as benzene,chlorobenzene, dichlorobenzene, cyclohexylbenzene, toluene, xylene, andmesitylene; ketones such as acetone, 2-butanone, and cyclohexanone;ethers such as tetrahydrofuran, diethyl ether, bis(2-methoxyethyl)ether,and dioxane; alcohols such as ethanol, propanol, and isopropyl alcohol;aliphatic hydrocarbons, such as hexanes; acetates, such as ethylacetate; halogenated aliphatic hydrocarbons such as dichloromethane,chloroform, and ethylene chloride; and other aprotic solvents such asdimethyl formamide and n-methyl pyrrolidone. As used herein, a compoundcan be considered soluble in a solvent when at least 1 mg of thecompound can be dissolved in 1 mL of the solvent.

Polymers of the present teachings can be used in various solution-phaseprocesses including, but not limited to, spin-coating, printing, dropcasting, dip coating, spraying, and blade coating. Spin-coating involvesapplying an excess amount of the coating solution onto a substrate, thenrotating the substrate at high speed to spread the fluid by centrifugalforce. The thickness of the resulting dielectric film prepared by thistechnique is dependent on the spin-coating rate, the concentration ofthe solution, as well as the solvent used. Printing can be performed,for example, with a rotogravure printing press, a flexo printing press,or an inkjet printer. The thickness of the dielectric film in thesecases will similarly be dependent on the concentration of the solution,the choice of solvent, and the number of printing repetitions. Ambientconditions such as temperature, pressure, and humidity, can also affectthe resulting thickness of the film. Depending on the specific printingtechniques used, printing quality can be affected by differentparameters including, but not limited to, rheological properties of theinks such as solubility and viscosity. For noncontact printingtechniques such as inkjet printing, the solubility requirement isgenerally less stringent and a solubility range as low as about 1-4mg/mL can suffice. For gravure printing, a higher solubility range maybe necessary, often in the range of about 50-100 mg/mL. Other contactprinting techniques such as screen-printing and flexo printing, canrequire even higher solubility ranges, for example, about 100-1000mg/mL.

One of the advantages of the polymers disclosed herein is their abilityto crosslink, for example, photocrosslink, after deposition onto asubstrate. The crosslinking functionality allows formation of a denselycrosslinked polymeric matrix. The crosslinked polymeric matrix is robustenough to withstand various conditions that are common in devicefabrication processes, including patterning and subsequentsolution-phase processes, for example, to form/deposit overlying layers(e.g., the semiconductor layer in a top-contact OFET). Without wishingto be bound to any particular theory, the crosslinking chemistry caninclude a 2+2 photo-stimulated cycloaddition that provides stablecyclobutane moieties. The crosslinking chemistry can also involve freeradical additions. Polymers of the present teachings can be cured, forexample, photocrosslinked, by exposure to ultraviolet light at, forexample, a wavelength of about 245 nm to 350 nm. Crosslinking can alsobe achieved by other types of radiation, for example, with ion beams ofcharged particles, and with radioactive sources. Subsequent to theformation of the crosslinked matrix, the dielectric material of thepresent teachings can be subject to further patterning and processsteps, by which additional layers, including additional dielectric,semiconductor and/or conducting layers, can be formed on top of thedielectric material.

Photopolymers of the present teachings can be used to prepare dielectricmaterials that can exhibit a wide range of desirable properties andcharacteristics including, but not limited to, low leakage currentdensities, high breakdown voltages, low hysteresis, large capacitance,uniform film thickness, solution-processability, fabricability at lowtemperatures and/or atmospheric pressures, air and moisture stability,and/or compatibility with diverse gate materials and/or semiconductors.

Leakage current density is typically defined as a vector whose magnitudeis the leakage current per cross-sectional area. As used herein,“leakage current” refers to uncontrolled (“parasitic”) current flowingacross region(s) of a semiconductor structure or device in which nocurrent should be flowing, for example, current flowing across the gateoxide in a metal-oxide-semiconductor (MOS) structure. As known by thoseskilled in the art, the leakage current density of a dielectric materialcan be determined by fabricating a standardmetal-insulator-semiconductor (MIS) and/or metal-insulator-metal (MIM)capacitor structures with the dielectric material, then measuring theleakage current, and dividing the measured current by the area of themetal electrodes.

Photopolymers of the present teachings and their crosslinked productscan have very low leakage current densities as measured from standardMIS and MIM capacitor structures. For example, photopolymers of thepresent teachings and their crosslinked products can have a leakagecurrent density of less than or equal to about 4×10⁻⁸ A/cm² at 2 MV/cm,less than or equal to about 2×10⁻⁸ A/cm² at 2 MV/cm, less than or equalto about 1×10⁻⁸ A/cm² at 2 MV/cm, less than or equal to about 8×10⁻⁹A/cm² at 2 MV/cm, less than or equal to about 7×10⁻⁹ A/cm² at 2 MV/cm,less than or equal to about 6×10⁻⁹ A/cm² at 2 MV/cm, less than or equalto about 4×10⁻⁹ A/cm² at 2 MV/cm, less than or equal to about 2×10⁻⁹A/cm² at 2 MV/cm, or less than or equal to about 1×10⁻⁹ A/cm² at 2MV/cm. Photopolymers of the present teachings also exhibit low leakagecurrent densities at higher voltages, for example, a leakage currentdensity of less than or equal to about 1×10⁻⁶ A/cm² at 4 MV/cm, lessthan or equal to about 5×10⁻⁷ A/cm² at 4 MV/cm, less than or equal toabout 3×10⁻⁷ A/cm² at 4 MV/cm, less than or equal to about 1×10⁻⁷ A/cm²at 4 MV/cm, less than or equal to about 5×10⁻⁸ A/cm² at 4 MV/cm, or lessthan or equal to about 1×10⁻⁸ A/cm² at 4 MV/cm.

Dielectric materials prepared from photopolymers of the presentteachings also were found to be able to withstand very high breakdownvoltages (i.e., the maximum voltage difference that can be appliedacross the dielectric before it breaks down and begins to conduct). Forexample, dielectric materials of the present teachings can withstand abreakdown voltage of 4 MV/cm or higher, a breakdown voltage of 6 MV/cmor higher, or a breakdown voltage of 7 MV/cm or higher.

Polymers of the present teachings also can have relatively low glasstransition temperatures. For example, polymers of the present teachingscan have a glass transition temperature of less than about 100° C., aglass transition temperatures of less than about 90° C., a glasstransition temperatures of less than about 80° C., a glass transitiontemperatures of less than about 70° C., a glass transition temperaturesof less than about 60° C., a glass transition temperatures of less thanabout 50° C., a glass transition temperatures of less than about 40° C.,or a glass transition temperatures of less than about 30° C. Inparticular embodiments, polymers of the present teachings can have aglass transition temperature in the range of about 30° C. to about 60°C. Glass transition temperature (T_(g)) can be defined as the mid-pointof a temperature range at which a material gradually becomes moreviscous and changes from a rubbery state to a glassy state. Due to thisproperty, dielectric materials deposited from polymers of the presentteachings can allow surface planarization and filling of pinholes beforecrosslinking, hence improving surface smoothness (for example, achievinga sub-nanometer surface roughness), and accordingly, device performanceand operation. Pinholes can also be filled by depositing two or morelayers of dielectric materials sequentially on top of one another, henceforming a multilayer dielectric material that can have very good surfaceuniformity and can be essentially pinhole-free over a large area.

The present teachings further provide articles of manufacture, forexample, composites, that includes a dielectric material of the presentteachings and a substrate component and/or a semiconductor component.The substrate component can be selected from, but is not limited to,doped silicon, an indium tin oxide (ITO), ITO-coated glass, ITO-coatedpolyimide or other plastics, aluminum or other metals alone or coated ona polymer or other substrate, a doped polythiophene, and the like. Thecomposite can include a semiconductor component. The semiconductorcomponent can be selected from, but is not limited to, various fusedheterocycles, polythiophenes, fused aromatics, and other such organicsemiconductor compounds or materials, whether p-type or n-type,otherwise known or found useful in the art. The semiconductor componentalso can include inorganic semiconductor materials such as silicon,germanium, gallium arsenide, and the like. The composite can include oneor more electrical contacts. Such electrical contacts can be made of ametal (e.g., gold) and can function as source, drain, or gate contacts.One or more of the composites described above can be embodied withinvarious organic electronic devices such as OTFTs, specifically, OFETs,as well as capacitors, complementary circuits (e.g., inverter circuits),and the like.

Another aspect of the present teachings relates to methods for preparinga dielectric material. The method can include preparing a solution thatincludes the polymer described herein, and printing the solution onto asubstrate to form a dielectric layer. The method can include exposingthe dielectric layer to a radiation source (e.g., ultraviolet light) toinduce crosslinking, thereby forming a crosslinked dielectric material.The method can also include printing an additional dielectric layer ontothe crosslinked dielectric layer to form a multilayer dielectricmaterial.

Another aspect of the present teachings relates to methods forfabricating organic field effect transistors that include a dielectricmaterial of the present teachings. The dielectric materials of thepresent teachings can be used to fabricate various types of organicfield effect transistors including, but not limited to, top-gatetop-contact capacitor structures, top-gate bottom-contact capacitorstructures, bottom-gate top-contact capacitor structures, andbottom-gate bottom-contact capacitor structures.

In some embodiments, the method can include preparing a solution thatincludes the polymer described herein, printing the solution onto asubstrate (gate) to form a dielectric layer, exposing the dielectriclayer to radiation to induce crosslinking to form a crosslinkeddielectric material, forming a semiconductor layer on the crosslinkeddielectric material, and forming a first electrical contact and a secondelectrical contact (source and drain) on the semiconductor layer, tofabricate a top-contact bottom-gate organic field effect transistor.

In other embodiments, the method can include preparing a solution thatincludes one or more polymers described herein, printing the solutiononto a substrate (gate) to form a dielectric layer, exposing thedielectric layer to radiation to induce crosslinking to form acrosslinked dielectric material, forming a first electrical contact anda second electrical contact (source and drain) on the crosslinkeddielectric material, and forming a semiconductor layer above the firstand second electrical contacts and the dielectric material (i.e., tocover the electrical contacts and an area of the dielectric materialbetween the electrical contacts), to fabricate a bottom-contactbottom-gate organic field effect transistor.

In some embodiments, the method can include forming a first electricalcontact and a second electrical contact (source and drain) on asubstrate, forming a semiconductor layer above the substrate and thefirst and second electrical contacts (to cover the electrical contactsand an area of the substrate between the electrical contacts), preparinga solution that includes one or more polymers described herein, printingthe solution onto the semiconductor layer to form a dielectric layer,exposing the dielectric layer to radiation to induce crosslinking toform a crosslinked dielectric material, forming a third electricalcontact (gate) on the crosslinked dielectric material, wherein the thirdelectrical contact is above an area between the first and secondelectrical contacts, to fabricate a bottom-contact top-gate organicfield effect transistor.

In other embodiments, the method can include forming a semiconductorlayer on a substrate, forming a first electrical contact and a secondelectrical contact (source and drain) on the semiconductor layer,preparing a solution that includes one or more polymers describedherein, printing the solution onto the first and second electricalcontacts and an area of the semiconductor layer between the first andsecond electrical contacts to form a dielectric layer, exposing thedielectric layer to radiation to induce crosslinking to form acrosslinked dielectric material, and forming a third electrical contact(gate) on the dielectric material, wherein the third electrical contactis above an area between the first and second electrical contacts, tofabricate a top-contact top-gate organic field effect transistor.

The semiconductor layer and the various electrical contacts can beformed by various deposition processes known to those skilled in theart. For example, the semiconductor layer can be formed by processessuch as, but not limited to, physical vapor deposition, different typesof printing techniques (e.g., flexo printing, litho printing, gravureprinting, ink-jetting, pad printing, and so forth), drop casting, dipcoating, doctor blading, roll coating, and spin-coating. Electricalcontacts can be formed by processes such as, but not limited to, thermalevaporation and radiofrequency or e-beam sputtering, as well as variousdeposition processes, including but not limited to those describedimmediately above (e.g., flexo printing, litho printing, gravureprinting, ink-jetting, pad printing, drop casting, dip coating, doctorblading, roll coating, and spin-coating).

In the following examples, polymers and dielectric materials accordingto the present teachings were prepared and characterized by NMR, IRspectroscopy, elemental analysis, differential scanning calorimetry(DSC), AFM, and metal-insulator-semiconductor (MIS) device leakage andimpedance spectroscopy measurements, to demonstrate, among other things,their dielectric properties and their compatibility with various p-typeand n-type organic semiconductors. Organic electronic devices, forexample, organic thin film transistors (OTFTs), specifically, organicfield effect transistors (OFETs), based on these dielectric films alsohave been fabricated and characterized, data of which are providedbelow.

The following examples are provided to illustrate further and tofacilitate the understanding of the present teachings and are not in anyway intended to limit the invention.

EXAMPLE 1 Preparation of poly(vinylphenylcinnamate) (PCyVP)

Poly(vinylphenol) (2.0 g, M_(w)=20,000 g/mol) was dissolved in 20 mL ofanhydrous tetrahydrofuran (THF), to which 5 mL of anhydroustriethylamine (excess) was added. The solution was placed in an ice bathfor 10 minutes, followed by addition of a solution of cinnamoyl chloride(5.25 g, excess) in 5 mL of anhydrous THF. After stirring overnight, thereaction mixture was filtered and the polymer precipitates were purifiedby repetitive precipitation to yield about 2.5 g ofpoly(vinylphenylcinnamate) (PCyVP) as a white powder.

¹H NMR (500 Mz, CDCl₃): δ 6.58-7.81 (m, 11H, aromatic and allylprotons), 0.6-1.8 (m, 3H, alkyl protons).

EXAMPLE 2 Preparation of poly(cinnamoylethylmethacrylate) [P(CyEMA)]

Poly(hydroxyethyl methacrylate) (2.0 g, M_(w)=20,000 g/mol, hydroxylgroup: 15.4 mmol) was dissolved in 20 mL of anhydrous pyridine. Thesolution was placed in an ice bath for 10 minutes, followed by additionof a solution of cinnamoyl chloride (6 g, 36 mmol) in 6 mL of anhydrousTHF. The reaction was stirred at room temperature overnight, thenprecipitated in about 200 mL of cold methanol (MeOH). The polymerprecipitates were purified by repetitive precipitation to yield about2.5 g of poly(cinnamoylethylmethacrylate) [P(CyEMA)] as a white solid.

¹H NMR (500 Mz, CDCl₃): δ 7.65(d, 1H, —CH═CH—), 7.51(s, broad, 2H,aromatic), 7.33(s, broad, 3H, aromatic), 6.45(d, 1H, —CH═CH—),4.09-4.28(m, 4H, OCH₂CH₂O), 2.06(s, sharp, 3H, OCH₃), 1.84-0.96 (m, 5H,CCH₃, —CH₂—).

EXAMPLE 3 Preparation of Random Copolymerpoly(vinylcinnamate-co-methylmethacrylate)[P(CyVP_(0.55)-co-MMA_(0.45))]

Poly(vinylphenol-co-methyl methacrylate) (10.0 g, M_(w)=8,000 g/mol,hydroxyl group: 50 mmol, vinylphenol moiety molar ratio 55% based oncalculation from proton NMR intergrations) was dissolved in 80 mL ofanhydrous THF, to which 9.6 mL of anhydrous triethylamine was added. Thesolution was placed in an ice bath for 10 minutes, followed by additionof a solution of cinnamoyl chloride (10.95 g, 66 mmol) in 30 mL ofanhydrous THF. The reaction was heated to 50° C. and stirred overnight,after which the reaction mixture was precipitated in 700 mL of coldMeOH. The precipitate was filtered, washed with MeOH, re-dissolved in100 mL of THF, and precipitated again. After further precipitation(three times in total), over 11 g of random copolymerpoly(vinylcinnamate-co-methylmethacrylate)[P(CyVP_(0.55)-co-MMA_(0.45))] were obtained as a white powder.

¹H NMR verified the copolymer ratio of cinnamoyl moiety and methacrylatemoieties as 55%:45%. ¹H NMR (500 Mz, CDCl₃): δ 6.63-7.84 (m, 11H,aromatic, —CH═CH—), 0.70-3.63 (m, 13H, alkyl protons). Elementalanalysis, found: C, 76.31%, H, 6.31%; calculated: C, 76.27%, H, 6.19%.

EXAMPLE 4 (COMPARATIVE EXAMPLE) Preparation of Random Copolymerpoly(vinylphenol-co-vinyl cinnamate-co-methylmethacrylate)[P(VP_(0.30)-co-CyVP_(0.25)-co-MMA_(0.45))]

Poly(vinylphenol-co-methyl methacrylate) (8.0 g, M_(w)=8,000 g/mol,hydroxyl group: 40 mmol, vinylphenol moiety molar ratio 55% based oncalculation from proton NMR intergrations) was dissolved in 60 mL ofanhydrous THF, to which 2.6 mL of anhydrous triethylamine was added. Thesolution was placed in an ice bath for 10 minutes, followed by additionof a solution of cinnamoyl chloride (3 g, 18 mmol) in 20 mL of anhydrousTHF. The solution was heated to 50° C. and stirred overnight, afterwhich the reaction mixture was filtered. The clear solution was placedunder vacuum to remove triethylamine and the solvent to give 8 g of arandom copolymer poly(vinylphenol-co-vinylcinnamate-co-methylmethacrylate)[P(VP_(0.30)-co-CyVP_(0.25)-co-MMA_(0.45))] as a pale yellow polymer.

¹H NMR verified the copolymer ratio of phenol, cinnamoyl andmethacrylate moieties as 30%, 25%, and 45%. ¹H NMR (500 Mz, dioxane-d8):δ 6.48-7.82 (m, 11H, aromatic, —CH═CH—), 0.64-2.98 (m, 8H, alkylprotons).

EXAMPLE 5 Preparation of High Molecular Weight Random Copolymerpoly(cinnamoylethyl methacrylate-co-acetoxyethyl methacrylate)[P(CyEMA_(0.50)-co-AcEMA_(0.50))]

Poly(hydroxyethyl methacrylate) (2.0 g, M_(w)=1,000,000 g/mol, hydroxylgroup: 15.4 mmol) was dissolved in 60 mL of anhydrous pyridine. Thesolution was placed in an ice bath for 10 minutes, followed by additionof a solution of cinnamoyl chloride (1.28 g, 7.7 mmol) in 4 mL ofanhydrous THF. The reaction was stirred at room temperature for 30minutes, after which 3 mL of acetic anhydride (excess) were added to capthe free OH groups on the polymer. The reaction was stirred at roomtemperature overnight, then precipitated in about 200 mL of cold MeOH.The polymer precipitates were purified by repetitive precipitation togive about 2 g of a high molecular weight random copolymerpoly(cinnamoylethyl methacrylate-co-acetoxyethyl methacrylate)[P(CyEMA_(0.50)-co-AcEMA_(0.50))] as a white solid.

¹H NMR verified the copolymer ratio as 50%:50%. ¹H NMR (500 Mz, CDCl₃):δ 7.71(s, broad, 1H, —CH═CH—), 7.57(s, broad, 2H, aromatic), 7.38(s,broad, 3H, aromatic), 6.51(s, broad, 1H, —CH═CH—), 4.12-4.37(m, 4H,OCH₂CH₂O), 2.06(s, sharp, 3H, OCH₃), 1.85-0.92 (m, 5H, CCH₃, —CH₂—).

EXAMPLE 6 Preparation of Random Copolymer poly(cinnamoylethylmethacrylate-co-acetoxyethylmethacrylate)[P(CyEMA_(0.57)-co-AcEMA_(0.43))]

Poly(hydroxyethyl methacrylate) (2.0 g, M_(w)=20,000 g/mol, hydroxylgroup: 15.4 mmol) was dissolved in 20 mL of anhydrous pyridine. Thesolution was placed in an ice bath for 10 minutes, followed by additionof a solution of cinnamoyl chloride (1.46 g, 8.76 mmol) in 4 mL ofanhydrous THF. The reaction was stirred at room temperature for 30minutes, after which 3 mL of acetic anhydride (excess) were added to capthe free OH groups on the polymer. The reaction was stirred at roomtemperature overnight, then precipitated in about 200 mL of cold MeOH.The polymer precipitates were purified by repetitive precipitation togive about 2 g of a random copolymer poly(cinnamoylethylmethacrylate-co-acetoxyethylmethacrylate)[P(CyEMA_(0.57)-co-AcEMA_(0.43))] as a white solid.

¹H NMR verified the copolymer ratio as 57%:43%. ¹H NMR (500 Mz, CDCl₃):δ 7.67(d, broad, 1H, —CH═CH—), 7.54(s, broad, 2H, aromatic), 7.36(s,broad, 3H, aromatic), 6.48(s, broad, 1H, —CH═CH—), 4.16-4.32(d, 4H,OCH₂CH₂O), 2.04(s, sharp, 3H, OCH₃), 1.85-0.92 (m, 5H, CCH₃, —CH₂—).

EXAMPLE 7 Preparation of Random Copolymer poly(cinnamoylethylmethacrylate-co-acetoxyethylmethacrylate)[P(CyEMA_(0.80)-co-AcEMA_(0.20))]

Poly(hydroxyethyl methacrylate) (3.0 g, M_(w)=20,000 g/mol, hydroxylgroup: 23 mmol) was dissolved in 30 mL of anhydrous pyridine. Thesolution was placed in an ice bath for 10 minutes, followed by additionof a solution of cinnamoyl chloride (3.07 g, 18.4 mmol) in 4 mL ofanhydrous THF. The reaction was stirred at room temperature for 6 hours,after which 3 mL of acetic anhydride (excess) were added to cap the freeOH groups on the polymer. The reaction was stirred at room temperatureovernight, then precipitated in about 200 mL of cold MeOH. The polymerprecipitates were purified by repetitive precipitation to give about 3 gof a random copolymer poly(cinnamoylethylmethacrylate-co-acetoxyethylmethacrylate)[P(CyEMA_(0.80)-co-AcEMA_(0.20))] as a white solid.

¹H NMR verified the copolymer ratio as 80%:20%. ¹H NMR (500 Mz, CDCl₃):δ 7.68(d, broad, 1H, —CH═CH—), 7.53(s, broad, 2H, aromatic), 7.35(s,broad, 3H, aromatic), 6.47(s, broad, 1H, —CH═CH—), 4.14-4.30(m, 4H,OCH₂CH₂O), 2.02(s, sharp, 3H, OCH₃), 1.83-0.93 (m, 5H, CCH₃, —CH₂—).

EXAMPLE 8 Preparation of Random Copolymer poly(cinnamoylethylmethacrylate-co-(trifluoroacetoxy)ethyl methacrylate)[P(CyEMA_(0.57)-co-TFAcEMA_(0.43))]

Poly(hydroxyethyl methacrylate) (2.0 g, M_(w)=20,000 g/mol, hydroxylgroup: 15.4 mmol) was dissolved in 20 mL of anhydrous pyridine. Thesolution was placed in an ice bath for 10 minutes, followed by additionof a solution of cinnamoyl chloride (1.46 g, 8.76 mmol) in 4 mL ofanhydrous THF. The reaction was stirred at room temperature for 3 hours,after which 3 mL of trifluoroacetic anhydride (excess) were added to capthe free OH groups on the polymer. The reaction was stirred at roomtemperature overnight, then precipitated in about 200 mL of cold MeOH.The polymer precipitates were purified by repetitive precipitation togive about 2 g of a random copolymer poly(cinnamoylethylmethacrylate-co-(trifluoroacetoxy)ethyl methacrylate)[P(CyEMA_(0.57)-co-TFAcEMA_(0.43))] as a white solid.

¹H NMR verified the copolymer ratio as 57%:43%. ¹H NMR (500 Mz, CDCl₃):δ 7.69(d, 1H, —CH═CH—), 7.54(s, broad, 2H, aromatic), 7.36(s, broad, 3H,aromatic), 6.47(broad, 1H, —CH═CH—), 3.73-4.33(m, 4H, OCH₂CH₂O),1.93-0.94 (m, 5H, CCH₃, —CH₂—).

EXAMPLE 9 Preparation of Random Copolymer poly(cinnamoylethylmethacrylate-co-(pentafluorobenzoyl)ethylmethacrylate)[P(CyEMA_(0.57)-co-F5BEMA_(0.43))]

Poly(hydroxyethyl methacrylate) (2 g, M_(w)=20,000 g/mol, hydroxylgroup: 15.4 mmol) was dissolved in 20 mL of anhydrous pyridine. Thesolution was placed in an ice bath for 10 minutes, followed by additionof a solution of cinnamoyl chloride (1.46 g, 8.76 mmol) in 4 mL ofanhydrous THF. The reaction was stirred at room temperature for 3 hours,after which 3 mL of pentafluorobenzoyl chloride (excess) were added tocap the free OH groups on the polymer. The reaction was stirred at roomtemperature overnight, then precipitated in about 200 mL of cold MeOH.The polymer precipitates were purified by repetitive precipitation togive about 2 g of a random copolymer poly(cinnamoylethylmethacrylate-co-(pentafluorobenzoyl)ethylmethacrylate)[P(CyEMA_(0.57)-co-F5BEMA_(0.43))] as a white solid.

¹H NMR verified the copolymer ratio as 57%:43%. ¹H NMR (500 Mz, CDCl₃):δ 7.64(d, 1H, —CH═CH—), 7.52(s, broad, 2H, aromatic), 7.35(s, broad, 3H,aromatic), 6.44(broad, 1H, —CH═CH—), 4.15-4.47(m, 4H, OCH₂CH₂O),0.88-1.83(m, 5H, CCH₃, —CH₂—).

EXAMPLE 10 Preparation of Random Copolymerpoly(3-(trifluoromethyl)-cinnamoylethylmethacrylate-co-acetoxyethylmethacrylate) [P(CF3CyEMA_(0.57)-co-AcEMA_(0.43))]

Poly(hydroxyethyl methacrylate) (2 g, M_(w)=20,000 g/mol, hydroxylgroup: 15.4 mmol) was dissolved in 20 mL of anhydrous pyridine. Thesolution was placed in an ice bath for 10 minutes, followed by additionof a solution of 3-trifluoromethyl cinnamoyl chloride (2.06 g, 8.76mmol) in 4 mL of anhydrous THF. The reaction was stirred at roomtemperature for 3 hours, after which 3 mL of acetic anhydride (excess)were added to cap the free OH groups on the polymer. The reaction wasstirred at room temperature overnight, then precipitated in about 200 mLof cold MeOH. The polymer precipitates were purified by repetitiveprecipitation to give about 2 g of a random copolymerpoly(3-(trifluoromethyl)-cinnamoylethylmethacrylate-co-acetoxyethylmethacrylate) [P(CF3CyEMA_(0.57)-co-AcEMA_(0.43))] as a white solid.

¹H NMR verified the copolymer ratio 57%:43%. ¹H NMR (500 Mz, CDCl₃): ¹HNMR (500 Mz, CDCl₃): δ 7.81-7.29(m, broad, 4H, aromatic, —CH═CH—),6.56(broad, 1H, —CH═CH—), 4.18-4.35(m, 4H, OCH₂CH₂O), 2.04(s, 3H, OCH₃)1.92-0.90 (m, 5H, CCH₃, —CH₂—).

EXAMPLE 11 Preparation of Capped poly(cinnamoylethylmethacrylate)[CAP-P(CyEMA)]

P(CyEMA) (3.0 g, Example 2) was dissolved in 30 mL of freshly distilledTHF and the resulting solution was cooled into an ice-water bath.Trifluoroacetic anhydride (0.5 g) was added dropwise under vigorousstirring in the absence of light. The reaction was warmed to ambienttemperature, stirred for 3 hours, and concentrated to dryness underreduced pressure. The resulted solid was dissolved in 30 mL freshlydistilled THF and the resulting solution cooled in an ice-water bath. Asecond portion of trifluoroacetic anhydride (0.5 g) was added dropwiseunder vigorous stirring. The reaction was warmed to ambient temperature,stirred overnight, and concentrated under reduced pressure. The residuewas dissolved in THF and precipitated by addition of methanol, dissolvedagain in THF and precipitated by addition of diethylether, and theresulting solid was dried under vacuum to provide CAP-P(CyEMA) as awhite foam (yield >95%).

EXAMPLE 12 Surface Morphology of Spin-Coated Dielectric Films

The photopolymers from Examples 1-3 were dissolved in dioxane to give asolution having a concentration of 80 mg/mL, respectively. The polymersolutions were then spin-coated onto clean silicon substrates between1300 rpm (acceleration 20). After the spin-coating step, the resultingdielectric films were treated in a 150 W ultraviolet oven for 10minutes, and then annealed in a vacuum oven at 100° C. for 10 minutes tocompletely remove any residual solvent. Film thickness and surfacesmoothness (represented by root mean square (RMS) roughness) weredetermined by profilometry and atomic force microscopy (AFM),respectively. The results showed that the polymer films of the presentteachings are very smooth, with RMS roughness being in the range ofabout 0.4 nm.

EXAMPLE 13 Dielectric Properties of Spin-Coated Dielectric Films

Metal-insulator-semiconductor (MIS) capacitor structures were fabricatedusing the resulting dielectric films from Example 11, and capacitance ofthe dielectric films was measured. For MIS structure fabrication,heavily doped n-type Si (MEMC Electronic Materials, Antimony/n-doped)was used as the semiconductor onto which the dielectric film wasspin-coated to form the insulating layer. Top Au electrodes (area 1=100μm×100 μm; area 2=200 μm×200 μm; area 3=500 μm×1000 μm; area 4=1000μm×1000 μm; area 5=1 cm×2 cm) were then vacuum deposited on top of thephotopolymer insulator at <1×10⁻⁶ Torr to complete the MIS capacitorstructure. Using a shadow mask, rectangular- or square-shaped Au padshaving a feature size ranging from 100 μm×100 μm to 1000 μm×1000 μm, canbe deposited to form MIS structures of different sizes. Unless otherwisespecified, leakage currents in this and following examples weredetermined using capacitor structures with Au pads having a feature sizeof 200 μm×200 μm. The J-E characteristics of capacitors based on thedielectric materials of the present teachings appear to be independentof the area of the Au pads, as shown in FIG. 1.

The current (I)-voltage (V) responses of the MIS structures weremeasured using a high sensitivity Keithley 6430 Sub-Femtoamp SourceMeter with Remote Preampifier, operated by a local Labview program andgeneral purpose interface bus communication. All of the measurementswere performed in ambient atmosphere (relative humidity=30-80%). Tominimize electrical noise during the I-V scan, a triaxial cabling andprobing system (Signatone, Gilroy, Calif.) was employed to probe the MISstructures. The combined use of the Signatone triaxial probing systemand the Keithley 6430 source meter reduced the noise level to as low as10⁻¹⁵ A and provided accurate current measurements as low as 10⁻¹⁴ A.During the measurement, the bottom electrode was probed with aninstrument ground and the top Au pads were probed with a soft tip fromthe Triaxial probe connected to the Keithley source meter. As controlledby the Labview program, an I-V scan was performed by applying bias tothe traixial probe and measuring current through the circuit. The scanrate was between 5-15 s/step, which was controlled by setting the delaytime to between 0.5 s and 2 s and the number of measurements per stepbetween 10 and 20.

The leakage current density (J) (I/area of Au pads) versus electricfield (E) (V/thickness of dielectric layer) plots are shown in FIG. 2.The J-E responses of dielectric films prepared from PVP, PMMA, and PCyVPare included for comparison.

Similar MIS capacitor structures and test procedures were used tocharacterize photopolymers from Examples 4 to 10. The leakage currentdensity (J) versus electric field (E) plots are shown in FIG. 3, alongwith comparison data from polymers of Examples 2 and 3. The dielectricproperties, i.e., leakage current density, capacitance (C_(i)), andbreakdown voltage (BV), as well as film thickness of the aforementionedexamples are summarized in Table 1.

TABLE 1 Dielectric properties of different photopolymer-based dielectricfilms. Leakage current Leakage current density (A/cm²) density (A/cm²)C_(i) Thickness BV Photopolymer at 2 MV/cm at 4 MV/cm (nF/cm²) (nm) (V)P(CyVP_(0.55)-co-MMA_(0.45)) 2 × 10⁻⁹ 1 × 10⁻⁸ 6.4 470 >200CAP-P(CyVP_(0.55)-co-MMA_(0.45)) 1 × 10⁻⁹ 4 × 10⁻⁹ 6.3 470 >200P(CP_(0.3)-co-CyVP_(0.25)-co-MMA_(0.45)) 3 × 10⁻⁸ 3 × 10⁻⁶ 6.8 440 >200P(CyEMA_(0.57)-co-AcEMA_(0.43)) 2 × 10⁻⁹ 6 × 10⁻⁸ 7.1 410 >200P(CyEMA_(0.8)-co-AcEMA_(0.2)) 2 × 10⁻⁹ 4 × 10⁻⁸ 7.3 400 >200 P(CyEMA) 2× 10⁻⁹ 1 × 10⁻⁸ 6.0 460 >200 CAP-P(CyEMA) 1 × 10⁻⁹ 4 × 10⁻⁹ 6.0 460 >200P(CyEMA_(0.57)-co-F5BEMA_(0.43)) 2 × 10⁻⁹ 1 × 10⁻⁸ 6.0 440 >200P(CF3CyEMA_(0.57)-co-AcEMA_(0.43)) 7 × 10⁻⁹ 2 × 10⁻⁷ 6.9 430 >200P(CyEMA_(0.57)-co-TFAcEMA_(0.43)) 6 × 10⁻⁹ 3 × 10⁻⁷ 6.9 480 >200P(CyEMA_(0.5)-co-AcEMA_(0.5)) (High MW) 4 × 10⁻⁹ 4 × 10⁻⁸ 7.8 400 >200PVP 6 × 10⁻⁷ Break down 6.5 570 150 V PMMA 7 × 10⁻⁹ 1 × 10⁻⁷ 12 250 >200PCyVP 2 × 10⁻⁸ 1 × 10⁻⁶ 9.5 300 >200 Crosslinkable polymerdielectrics >1 × 10⁻⁷  N/A N/A N/A N/A reported in the literature

EXAMPLE 14 Device Performance of Pentacene-Based OFETs Fabricated withSpin-Coated Dielectric Films

Pentacene OFETs were fabricated with dielectric films from Examples 11and 12 on both silicon and aluminium gate materials. Specifically, thesilicon substrates were highly n-doped silicon wafers obtained fromMontco Silicon Tech, Inc. (Spring City, Pa.) and cleaned by sonicationin organic solvents before use. The aluminium substrates were cut fromAl-coated plastic substrates. Pentacene was purchased from Sigma-Aldrich(St. Louis, Mo.) and vacuum-deposited at about 2×10⁻⁶ Torr (500 Å, 0.3Å/s) while maintaining the substrate temperature at about 50° C. toabout 70° C. Gold (Au) electrodes were vacuum-deposited through shadowmasks at 3-4×10⁻⁶ Torr (500 <, 0.3 Å/s). The channel length was 50 μm,and the channel width was 5000 μm. These OFETs were found to performvery well, with mobility (μ) approximating 0.5 cm²/Vs, an I_(on):I_(off)ratio up to 2×10⁷, negligible hysteresis, and extremely low gate leakagecurrents. Representative OFET transfer and output plots are shown inFIG. 4 (P(CyEMA_(0.57)-co-F5BEMA_(0.43)) is used as the dielectriclayer). OFET performances of these photopolymer-based devices aresummarized in Table 2. A comparative pentacene OFET device wasfabricated using silicon oxide (SiO₂) as the dielectric material. Thesilicon oxide film has a thickness of 300 nm. The carrier mobilities ofthis comparative device were found to be about 0.1 cm²/Vs to about 0.3cm²/Vs.

TABLE 2 Pentacene field-effect transistor parameters for TFT devicesbased on polymeric dielectric materials of the present teachings.(*Carrier mobility was calculated in saturation.) Gate Sub- μ leakagePolymer # strate (cm²/Vs) I_(on):I_(off) (nA)P(CyVP_(0.55)-co-MMA_(0.45)) Si 0.3 2 × 10⁶ 10P(CP_(0.3)-co-CyVP_(0.25)-co-MMA_(0.45)) Si 0.3 2 × 10⁶ 100P(CyEMA_(0.57)-co-AcEMA_(0.43)) Si 0.8 1 × 10⁶ 100P(CyEMA_(0.8)-co-AcEMA_(0.2)) Si 0.7 3 × 10⁶ 40 P(CyEMA) Si 1.0 2 × 10⁷3 CAP-P(CyEMA) Si 1.2 4 × 10⁷ 2 P(CyEMA_(0.57)-co-F5BEMA_(0.43)) Si 1.21 × 10⁷ 1000 P(CF3CyEMA_(0.57)-co-AcEMA_(0.43)) Si 0.3 5 × 10⁵ 10P(CyEMA_(0.57)-co-TFAcEMA_(0.43)) Si 0.6 2 × 10⁶ 20P(CyEMA_(0.8)-co-AcEMA_(0.2)) Al 0.32 1 × 10⁶ 1 PCyVP Si 0.65 1 × 10⁵10000 SiO₂ Si 0.2 1 × 10⁶ 10

EXAMPLE 15 Device Performance of n-type OFETs Fabricated withSpin-Coated Dielectric Films

A perylene-type n-type semiconductor,N,N′-bis(n-octyl)-dicyanoperylene-3,4:9,10-bis(dicarboximide) (PDI-8CN₂)was used to fabricate n-type OFET devices with photopolymers of thepresent teachings as the dielectric layer. Specifically, the siliconsubstrates were highly n-doped silicon wafers obtained from MontcoSilicon Tech, Inc. (Spring City, Pa.) and cleaned by sonication inorganic solvents before use. PDI-8CN₂ was synthesized according toprocedures described in U.S. Patent Application Publication No.2005/0176970, and vacuum-deposited at about 2×10⁻⁶ Torr (500 Å, 0.3 Å/s)while maintaining the substrate temperature at about 100° C. to about110° C. Au electrodes were vacuum-deposited through shadow masks at3-4×10⁻⁶ Torr (500 Å, 0.3 Å/s). The channel length was 50 μm, and thechannel width was 5000 μm. These OFETs were found to perform very well,with n-type mobility (μ) approximating 0.05 cm²/Vs, an I_(on):I_(off)ratio up to 1×10⁴, negligible hysteresis, and minimal gate leakagecurrents. Representative OFET transfer and output plots are shown inFIG. 5 (P(CyVP_(0.55)-co-MMA_(0.45)) is used as the dielectric layer).

EXAMPLE 16 Solubility of Photopolymer Materials Before and AfterPhotocrosslinking

Many photopolymers of the present teachings are soluble in commonorganic solvents including, but not limited to, tetrahydrofuran,bis(2-methoxyethyl) ether, dioxane, chloroform, ethyl acetate, acetone,toluene, dichlorobenzene, cyclohexylbenzene, dimethylformamide, n-methylpyrrolidone, and cyclohexanone. Photopolymers from Examples 1-10, forexample, have excellent solubility in common organic solvents. Forinstance, P(CyEMA) from Example 2 can be dissolved in ethyl acetatewithout heating to give a solution having a concentration of 350 mg/mL.Such a solution is sufficiently viscous for use in gravure printing.

After printing or other solution-phase depositing steps, photopolymersof the present teachings can be cured by exposure to ultraviolet light(e.g., via treatment in a 150 W UV oven for 10 minutes), which rendersthem insoluble in the organic solvents in which they were initiallysoluble prior to the photocrosslinking step. The cured dielectric filmswere found to be robust enough to withstand relatively harsh processes.For example, a photocrosslinked dielectric film was sonicated indichlorobenzene for 5 minutes, after which its thickness and physicalappearance was found to be substantially the same as before thesonication step. This feature of the present dielectric materials makesthem attractive candidates for solution-processed bottom-gate OFETs,which requires that the dielectric layer be insoluble in thesolution-processing solvent (e.g., dichlorobenzene) for the depositionof the semiconductor layer.

EXAMPLE 17 Multilayer Dielectric Material Fabricated with Spin-CoatedPhotopolymer Materials

Since photopolymers of the present teachings can become insoluble incommon organic solvents after photocrosslinking, multiple layers ofdielectric materials can be coated on top of one another withoutdissolving the earlier deposited layers. Such multilayer dielectricstructures can offer many performance advantages including, but notlimited to, minimized pinholes and better uniformity over larger areas.

MIS capacitor structures and test procedures similar to those describedin Example 12 were prepared and used to characterize a two-layerdielectric material prepared from P(CyVP_(0.55)-co-MMA_(0.45)) (Example3). The leakage current density (J) versus electric field (E) plot isshown in FIG. 6. While the test pixel shown in FIG. 9 has a relativelylarge area of about 2 cm² (typical OFET devices and MIS structures havetest pixels generally smaller than 0.01 cm²), the leakage currentdensity of the tested two-layer dielectric films is still extremely low,indicating excellent film uniformity over large areas. The thickness ofthe two-layer dielectric film was about 1000 nm, which is two timesthicker than the single-layer films (500 nm) of Example 11, implicatingthe insolubility of the photocrosslinked film during the multilayercoating process.

Pentacene OFETs were fabricated with the two-layer dielectric filmsdescribed above. These pentacene OFETS exhibited excellent deviceperformance, as evidenced by hole mobility (μ) of about 0.22 cm²/Vs,I_(on):I_(off) ratio of about 3×10⁷, negligible hysteresis, and gateleakage current as low as 3 nA at 180 V gate bias. The transfer andoutput plots are shown in FIG. 7.

EXAMPLE 18 Printability of Dielectric Compositions ContainingPhotopolymers

Using the photopolymer P(CyEMA_(0.80)-co-AcEMA_(0.20)) of Example 7,printable dielectric layers were fabricated. The photopolymer wasdissolved in ethyl acetate to give a solution having a concentration of300 mg/mL solution. Dielectric films were printed using the printingpress (IGT), using the gravure mode and the following parameters: Aniloxforce 100 N, printing speed 0.4 m/s, anilox cylinder 402.100 (40 l/cm,copper engraved-chromium plated, stylus 130°, screen angle 53, volume23.3 mL/m²). A first layer of the photopolymer was printed on Al-PENsubstrate, UV cured for 10 minutes and dried in a vacuum oven for 10minutes. A second layer of the photopolymer was printed onto the firstlayer and cured in the same way. MIS capacitor structures and pentaceneOFETs were subsequently fabricated. The output and transfer plots of thepentacene OFETs are shown in FIG. 8.

EXAMPLE 19 UV Curing of the Photopolymers

Selected photopolymers of the present teachings were crosslinked byexposure to ultraviolet light at 254 nm. IR spectroscopy was used toconfirm the photocrosslinking of these polymers. The double bond in thecinnamoyl group exhibited characteristic IR absorption at 1630 cm⁻¹before photocrosslinking, and disappeared after the 2+2 cycloadditionphotocrosslinking reaction as predicted. FIG. 9 shows the IR absorptionspectrum for a photopolymer film before and after UV curing. It could beseen that the intensity of the C═O stretching is significantly reducedafter the UV treatment.

EXAMPLE 20 Low Glass Transition Temperature of the Present Photopolymers

The glass transition properties of the present photopolymers werecharacterized by differential scanning calorimetry (DSC). FIG. 10 showsa typical DSC plot of photopolymers of the present teachings. Additionaldata for some of the photopolymers are summarized in Table 3. Forexample, the glass transition temperature (T_(g)) ofP(CyEMA_(0.57)-co-AEMA_(0.43)) was measured to be about 45° C. (comparedto conventional polymeric dielectric material such as PMMA, which hasT_(g) between 80-100° C.). Such low glass transition temperature allowsa time period for achieving surface planarization and filling ofpinholes before initiating the photocrosslinking step to obtain thefinal photocured crossinked dielectric matrix, which can explain thegood film forming properties of photopolymers of the present teachings.Polymers with lower glass transition temperatures (e.g. PMMA, which hasT_(g) between about 80-100° C.) typically have better film formingproperties compared to polymers with higher glass transitiontemperatures (e.g., PVP, which has a T_(g) over 150° C.).

TABLE 3 Glass transition temperatures. Polymer Tg (° C.) Poly(vinylphenol), PVP 150 Poly(methylmethacrylate), PMMA 80-100Poly(vinylphenylcinnamate), PCyVP (Example 1) 100 P(CyEMA) (Example 2)53 P(CyEMA_(0.57)-co-AcEMA_(0.43)) (Example 6) 45P(CyEMA_(0.57)-co-F5BEMA_(0.43)) (Example 9) 56 CAP-P(CyEMA) (Example11) 53

EXAMPLE 21 Shelf Stability of Photopolymer Dielectric Films

FIG. 11 shows the leakage current density versus electric field (J-E)plot of an MIS capacitor structure incorporating a dielectric filmprepared from (P(CyVP_(0.55)-co-MMA_(0.45)) that had been stored in airfor 55 days. It can be seen that, despite the storage period, thephotopolymer dielectric film still exhibited excellent dielectricproperties, as evidenced by the very low the leakage current density(which actually decreased slightly after 55 days). These resultstherefore show that the present photopolymer materials possess excellentshelf stability as a dielectric material. As it is recognized, OHgroup-containing dielectric polymers are typically moisture-sensitiveand have limited shelf stability. Without wishing to be bound to anyparticular theory, it is believed that by derivatizing the photopolymersto decrease the number of OH groups present, photopolymers of thepresent teachings have improved shelf stability compared to other knownpolymer dielectric materials such as PVP. Residual OH groups can becapped or masked, for example, by using suitable reagents, includingtrifluoroacetic anhydride (e.g., Example 11) or trifluoroacetylchloride.

EXAMPLE 22 Exclusively Solution-Processed OFET

Completely solution-processed OFETs were fabricated using photopolymersof the present teachings as the dielectric layer and a drop-castedn-type perylene material as the semiconductor layer. It is believed thatthis was the first n-type OFET device fabricated that had both thesemiconductor layer and the dielectric layer deposited from solution.

A perylene-based n-type semiconductor,N,N′-bis(n-octyl)-dicyanoperylene-3,4:9,10-bis(dicarboximide)(PDI-8CN₂), was dropcasted from a dichlorobenzene solution (2 mg/mL) ona solution-deposited and then crosslinked photopolymer dielectric layer(700 nm) on a Si substrate. The substrate was maintained at 105° C.,during which the solvent was evaporated to yield a crystallinesemiconductor film. OFET devices were fabricated and tested usingprocedures similar to those described in the previous examples.Representative transfer and output plots are shown in FIG. 12. Theexclusively solution-processed OFETs exhibited good device performance:N-type mobility was calculated to be as high as 0.035 cm²/Vs,I_(on):I_(off) ratio was measured to be about 1×10⁴, and gate leakagecurrent was measured to be less than or about 50 nA. These results showthat the present photopolymer-based dielectric materials have excellentinsolubility against the solvents used in the solution processes used todeposit the semiconductor layer, and that the present photopolymer-baseddielectric materials have good compatibility with solution-processedn-type semiconductor materials.

EXAMPLE 23 Photopolymer Dielectric Thin Films

FIG. 13 shows the J-E plot of a 100 nm thick photopolymer dielectricfilm. The data presented in FIG. 14 show comparable leakage currentdensity compared to the 400 nm to 500 nm photopolymer dielectric filmsdemonstrated in the earlier examples. It can be seen that the breakdownfield of such a thin film can be as high as 7 MV/cm.

EXAMPLE 24 Effect of OH Groups in Photopolymer Structures on LeakageCurrent Density

The leakage current density vs electric field plots ofP(CyVP_(0.55)-co-MMA_(0.45)) (Example 3) andP(VP_(0.30)-co-CyVP_(0.25)-co-MMA_(0.45)) (Example 4) are compared inFIG. 14. It can be seen that the leakage current density ofP(CyVP_(0.55)-co-MMA_(0.45)) is about two orders of magnitude lower thatof P(VP_(0.30)-co-CyVP_(0.25)-co-MMA_(0.45)). Since a main differencebetween the two polymers is thatP(VP_(0.30)-co-CyVP_(0.25)-co-MMA_(0.45)) has significant amount of OHgroups while P(CyVP_(0.55)-co-MMA_(0.45)) has almost none, these datasuggest that OH groups can have dramatic effect on the leakage currentdensity of dielectric polymers. Additional capping or masking of theresidual OH groups (e.g., Example 11) can further reduce leakage currentdensity and stabilize electrical performance under ambient conditions.

EXAMPLE 25 Effect of Photo-Patterning on Dielectric Properties

A spincoated photopolymer film [P(CyEMA) in Example 2] was exposed toultraviolet light (254 nm) through a shadow mask and then washed withTHF and dried. The film exhibited a clear pattern negative to that ofthe shadow mask. Au electrodes were then evaporated on top of theexposed and crosslinked region of the film to fabricate an MIS capacitorstructure, the leakage current of which was tested using similarprocedures as described earlier. FIG. 15 shows the leakage currentdensity vs electric field plot of such a dielectric film. The J-Eresponse of a similar dielectric film without any photopatterning/solvent rinsing treatment also was shown in the figure forcomparison. It can be seen that the leakage current of the patterneddielectric film was comparable to the unpatterned dielectric film.

In another experiment, parallel Au lines were deposited on a Sisubstrate, after which a photopolymer film [P(CyEMA) in Example 2] wasspincoated on top of the Au lines. The photopolymer film was exposed toultraviolet light (254 nm) through a shadow mask with line-shapeopenings perpendicular to the underlying Au lines. The photopolymer filmwas washed with THF and dried. The resulting film has rectangular-shaped“via holes” at the intersections of Au lines and photo mask lines. Totest if the “via holes” were free of photopolymer residues, anotherlayer of Au electrode was deposited on top the “via holes” and theinterconnect resistance at the “via holes” was estimated to be <5 ohm.

These two experiments show that the photopolymer dielectric materialscan be easily integrated with circuitry fabrication processes, includingphoto patterning and “via hole” patterning processes.

EXAMPLE 26 Bottom-Contact Bottom-Gate OFETs with a PhotopolymerDielectric Layer

FIG. 16 illustrates the four common types of OFET structures:top-contact bottom-gate structure (a), bottom-contact bottom-gatestructure (b), bottom-contact top-gate structure (c), and top-contacttop-gate structure (d). As shown in FIG. 16, an OFET can include adielectric layer (e.g., shown as 8, 8′, 8″, and 8′″ in FIGS. 16 a, 16 b,16 c, and 16 d, respectively), a semiconductor layer (e.g., shown as 6,6′, 6″, and 6′″ in FIGS. 16 a, 16 b, 16 c, and 16 d, respectively), agate contact (e.g., shown as 10, 10′, 10″, and 10′″ in FIGS. 16 a, 16 b,16 c, and 16 d, respectively), a substrate (e.g., shown as 12, 12′, 12″,and 12′″ in FIGS. 16 a, 16 b, 16 c, and 16 d, respectively), and sourceand drain contacts (e.g., shown as 2, 2′, 2″, 2′″, 4, 4′, 4″, and 4′″ inFIGS. 16 a, 16 b, 16 c, and 16 d, respectively). Most of the OFETdevices demonstrated in the previous examples have top-contactbottom-gate structures. In this example, bottom-contact bottom-gateOFETs were fabricated using a dielectric material of the presentteachings [P(CyEMA) in Example 2] as the insulating layer. First, adielectric film was fabricated on a Si substrate with a thickness ofabout 900 nm. Au (25 nm) was evaporated onto the photopolymer filmthrough a shadow mask to form source and drain electrodes, which werethen treated in saturated alkylthiol ethanol solution for 1 hour.Pentacene (50 nm) was then evaporated on top (the substrate temperaturewas 60° C.) to complete the bottom-contact device. The transfer andoutput plots of such a bottom-contact device are shown in FIG. 17. Holemobility of about 0.074 cm²/Vs and an I_(on)/I_(off) ratio of about1×10⁷ were obtained.

EXAMPLE 27 Bottom-Contact Top-Gate OFETs with a Photopolymer DielectricLayer

In this example, bottom-contact top-gate OFETs were fabricated using adielectric material of the present teachings [P(CyEMA) from Example 2]as the dielectric layer. First, Au (25 nm) was evaporated onto aninsulating substrate (SiO₂) through a shadow mask to form source anddrain electrodes, which were then treated in saturated alkylthiolethanol solution for 1 hour. Second, pentacene (50 nm) was evaporated ontop to form the semiconductor layer. Photopolymer films were thenspin-coated on top of pentacene as the dielectric layer followed bydeposition of Au as the gate electrode. The transfer plot of such abottom-contact top-gate device is shown in FIG. 18. Hole mobility ofabout 0.01 cm²/Vs and an I_(on)/I_(off) ratio of about 3×10³ wereobtained.

EXAMPLE 28 Top-Contact OFETs with a Photopolymer Dielectric Layer and aConducting Polymer as the Bottom-Gate Electrode

In this example, top-contact OFETs were fabricated using a dielectricmaterial of the present teachings [P(CyVP_(0.55)-co-MMA_(0.45)) fromExample 3] as the dielectric layer and a conducting polymer thin film asthe bottom-gate electrode. First, a conducting polymer (PEDOT-PSS, 1:1ratio) was spin-coated on a 3M™ overhead transparency to form the gateelectrode. Dielectric and semiconductor layers (n-type semiconductor,N,N′-bis(n-octyl)-dicyanonaphthalene-3,4:9,10-bis(dicarboximide),NDI-8CN₂) were then deposited using procedures similar to thosedescribed in Example 14. Au (25 nm) was evaporated onto thesemiconductor layer to complete the top source and drain electrodes. TheOFET characteristics (output plot) of such a top-contact bottom-gatedevice are shown in FIG. 19. Electron mobility of about 0.03 cm²/Vs andan I_(on)/I_(off) ratio of about 10 were obtained.

The present teachings can be embodied in other specific forms withoutdeparting from the spirit or essential characteristics thereof. Theforegoing embodiments are therefore to be considered in all respectsillustrative rather than limiting on the present teachings describedherein. The scope of the present teachings is thus indicated by theappended claims rather than by the foregoing description, and allchanges that come within the meaning and range of equivalency of theclaims are intended to be embraced therein.

1. An organic thin film transistor comprising a semiconductor layer, apolymeric layer in contact with the semiconductor layer, a gateelectrode, a source electrode and a drain electrode, wherein thesemiconductor layer comprises an organic semiconductor compound, and thepolymeric layer comprises a photocrosslinked product of a homopolymer ofthe repeating unit:

wherein R¹ and R² independently are selected from H and F; and theorganic thin film transistor exhibits a mobility of at least about 0.01cm²/Vs and an I_(on)/I_(off) ratio of at least about 10³.
 2. The organicthin film transistor of claim 1, wherein R¹ is F and R² is H.
 3. Theorganic thin film transistor of claim 1, wherein R¹ is H and R² is F. 4.The organic thin film transistor of claim 1, wherein each of R¹ and R²is H.
 5. The organic thin film transistor of claim 1, wherein each of R¹and R² is F
 6. The organic thin film transistor of claim 1, wherein thedevice is an organic field-effect transistor (OFET).
 7. The organic thinfilm transistor of claim 6, wherein the device is a bottom-contactbottom-gate OFET.
 8. The organic thin film transistor of claim 6,wherein the device is a bottom-contact top-gate OFET.
 9. The organicthin film transistor of claim 1, wherein the polymeric layer isdeposited on a substrate, and the semiconductor layer is deposited onthe polymeric layer.
 10. The organic thin film transistor of claim 9,wherein the substrate is selected from indium tin oxide (ITO),ITO-coated glass, and ITO-coated polyimide.
 11. An organic thin filmtransistor comprising a semiconductor layer, a polymeric layer incontact with the semiconductor layer, a gate electrode, a sourceelectrode and a drain electrode, wherein the semiconductor layercomprises an organic semiconductor compound, and the polymeric layercomprises a photocrosslinked product of a copolymer of repeating units:

wherein R¹ and R² independently are selected from H and F; and theorganic thin film transistor exhibits a mobility of at least about 0.01cm²/Vs and an I_(on)/I_(off) ratio of at least about 10³.
 12. Theorganic thin film transistor of claim 11, wherein R¹ is F and R² is H.13. The organic thin film transistor of claim 11, wherein R¹ is H and R²is F.
 14. The organic thin film transistor of claim 11, wherein each ofR¹ and R² is H.
 15. The organic thin film transistor of claim 11,wherein each of R¹ and R² is F.
 16. The organic thin film transistor ofclaim 11, wherein the device is an organic field-effect transistor(OFET).
 17. The organic thin film transistor of claim 16, wherein thedevice is a bottom-contact bottom-gate OFET.
 18. The organic thin filmtransistor of claim 16, wherein the device is a bottom-contact top-gateOFET.
 19. The organic thin film transistor of claim 11, wherein thepolymeric layer is deposited on a substrate, and the semiconductor layeris deposited on the polymeric layer.
 20. The organic thin filmtransistor of claim 19, wherein the substrate is selected from indiumtin oxide (ITO), ITO-coated glass, and ITO-coated polyimide.